1. Field of the Invention
This invention relates to an enclosed switchboard such as a motor control center or the like.
2. Background of the Invention
Generally in an enclosed switchboard such as a motor control center or the like, plural unit chambers are constructed by a vertically partitioned box-like frame with shelf plates for several stages, and control units are housed in these unit chambers so that they are drawably placed. On the common frame of such control units are arranged various kinds of control devices such as circuit breakers, electromagnetic contactors, control relays, etc., and their connecting circuits are so composed that intended control functions can be obtained. The main circuit, or occasionally the control circuit thereof is so constructed as to automatically connect to and disconnect from the corresponding circuit on the panel frame side by a put-in and a pull-out operation relative to the switchboard frame.
Contacts are so arranged on the rear of the control unit that putting in the control unit brings a power contact into connection with a bus bar (generally vertical bus bars) arranged on the panel frame of the switchboard, through which power is supplied to equipment mounted on the switchboard. This also brings load contacts into connection with the load side terminals, thereby power is supplied to the load side with switching on and off by way of the control unit.
An enclosed switchboard provided with such drawer type control units is so designed that the front door of the panel frame can be closed only with the units in their inserted positions. Meanwhile, in the test and disconnected positions with the contacts drawn out of the bus bars, the control units project from the front of the panel frame, preventing the door from being closed.
In the conventional switchboard described above, the door can not be closed in the disconnect and test positions but can be closed in the connect position, necessitating that the door be left open while checking the interior in the testing position or in the disconnected position. However, leaving the door open impairs the enclosed function of the switchboard, allowing for electric shock and other dangers due to the blowing emission of arcs and substances out of the switchboard in case of accidents. It may also block the passage and hamper operators from passing through, sometimes causing injuries or damage due to accidental bumping.
Thus, for the above reasons, it is very inconvenient in such conventional enclosed switchboards when the control unit is not placed in the connected position for a long time, for example when the control units must be removed and stored at some location, to close the door so as not to block the passage in front of the switchboard.
In order to solve the problems described above, there has been proposed an enclosed switchboard which is described hereinafter and which is disclosed in Japanese patent application No. 61-180743 and U.S. Pat. No. 4,860,161 issued Aug. 23, 1989.
Namely, FIGS. 15 and 16 are a horizontal plane view and a front view of such an enclosed switchboard. In these figures, numeral 1 indicates a panel frame constituting the boxlike body of the switchboard, numeral 2 indicates shelves fixed to the panel frame, and numerals 3 and 4 are doors. The shelves 2 are fitted with guide frames 2a. A unit frame 5 provided with various pieces of equipment is disposed on the guide frames 2a and is inserted from the front of the panel frame 1. The numeral 6 is a roller fitted to permit easy mounting of the unit frame 5 with a slight force. The unit frame 5 has a contact mounting frame 9 equipped with a power contact 7 and a load contact 8 and is so mounted on the rear as to travel in the connecting and disconnecting directions of such contacts 7 and 8, i.e., in the forward and backward direction thereof. The contacts 7 and 8 are wired using wires (not shown) with the equipment mounted on the frame 5.
The panel frame 1 has a bus bar 10 of such as a 3-phase 4-wire system and a load-side terminal 11 to which the power contact 7 and the load contact 8 are to be connected respectively.
Lock pins 12 (FIGS. 15, 17a, 17b) are set up at two points on the shelf plate 2. When the unit frame 5 is inserted in the shelf plate 2, these lock pins 12 are so disposed that a hook 13 of which an intermediate portion is rotatably mounted by means of an axis 13a and on which a groove 13b is provided on the front side (in the clockwise direction) of the hook 13 is engaged with the lock pins 12 so as to prevent removal of the unit frame 5 from the panel frame 1. The numeral 14 indicates a spring for energizing the hook 13 in a clockwise direction to retain the engagement thereof and 13c is a release lever operable to cancel the engagement thereof.
As shown in FIG. 17a, the hook 13 has a projection 13d, a concave portion 13e, and a straight portion 13f formed on the back, which operate together with an actuator 24 fixed at the side of the contact mounting frame 9. When the contact mounting frame 9 is disconnected from the unit frame, as shown in FIG. 17(a), the actuator 24 forces the projection 13c against the energizing force of the spring 14, causing the hook 13 to slightly pivot around the axis 13a and thereby withdraw a little from the lock pin 12. Under this condition, putting in the unit frame 5 together with the contact mounting frame 9 along the shelf 2 causes the lock pin 12 shown in a dot-dash line in FIG. 17(a) to come into contact with the cam slant 13g of the hook 13, move the hook 13 at a slight incline to the left, and finally engage with the groove 13b thereof as shown in a solid line. The unit frame 5 may be smoothly removed from the shelf 2 by pulling the frame 5 with the release lever 13c pushed by hand to the state shown in the dot-dash line, which releases the engagement between the lock pin 12 and the hook 13.
When the contact mounting frame 9 is in the test or connected position in relation to the unit frame 5, the possible insertion of the unit frame 5 along the shelf 2 will lead to the direct connection of the contacts to the power source, which could prove to be dangerous. Pulling out of the unit frame 5 from the shelf 2 in the test or connected position is also dangerous. Therefore, the construction is such that, when the contact frame 9 is in the test and connected positions in relation to the unit frame 5, as shown in FIG. 17(b), the actuator 24 is in contact with the straight portion 13f of the hook 13 on the back. In FIG. 17(b) the actuator 24 is shown in the test position by the solid line, and in the connected position by the dot-dash line. While the contact mounting frame 9 is positioned in such a relation with the unit frame 5, the hook 13 cannot be pivoted by the actuator 24, thus enabling the hook 13 to prevent the lock pin 12 fixed on the shelf 2 from being engaged or disengaged. Accordingly, in the state shown in FIG. 17(b) the unit frame 5 is prevented from being inserted in the shelf 2 as well as being prevented from being removed in spite of pushing of the release lever 13c. In this way the loading and unloading of the unit frame is allowed only in the disconnected position of the contacts, thereby enhancing safety.
The unit frame 5 is fitted with an interlocking arm 16 rotatably mounted around an interlocking arm axis 15 fixed to the unit frame 5 for driving the contacts, while the contact mounting frame 9 is furnished with a driving shaft 17, which is inserted in a slot 16a disposed at the edge of the interlocking arm 16 for floating engagement therein. An operating rod 19 is fixed at the base of the interlocking arm 16 for engaging the operating lever 18 and which moves the contact mounting frame 9 to its test and connected positions. The edge of the operating rod 19 faces a slot 5b (FIG. 16) in a grip frame 5a at the front of the unit frame 5.
The operating rod 19 contains a lock collar 21 (FIG. 22), urged forward by a spring 20, and having a guide hole 21a in the center thereof in which the end of the operating lever 18 shown in FIG. 18 is inserted. The operating lever 18 consists of the inserting portion 18a, a collar 18b, a small diameter portion 18c and a grip 18d. The grip 18d has a rubber coating. The inserted end 18a has a diameter larger than the width of the slot 5b of the grip frame 5a shown in FIG. 16 and smaller than the diameters of notches 5b-1, 5b-2, and 5b-3. The diameter of the small diameter portion 18c is smaller than the width of the slot 5b. The diameter of the collar 18b is larger than that of the guide hole 21a in the lock collar 21, larger than the width of the slot 5b of the grip frame 5a, and smaller than the diameters of the notched portions 5b-1, 5b-2, and 5b-3. Thereby the operating lever 18 can not be inserted at any other position of the slot 5b than the notched portions 5b-1, 5b-2 and 5b-3. Once the operating lever 18 has been inserted in, the lock collar 21, it can not be removed from the slot at any intermediate position but can be removed only at the notched portions 5b-1, 5b-2 and 5b-3. In addition, at these notched portions 5b-1, 5b-2 and 5b-3, the tip end of the lock collar 21 is such that it projects forwardly due to the energizing force of the spring 20.
The lock collar 21 has its end of a diameter slightly smaller than those of the notches 5b-1, 5b-2, and 5b-3, thereby permitting the collar 21 when projected as mentioned above to engage with the notches and lock.
Thus, turning the operating lever 18, the end thereof being inserted in the lock collar 21, clockwise in the drawing moves the contact unit 9 to its test and connected positions. Referring to FIG. 16 the three notches of a larger diameter 5b-1, 5b-2, and 5b-3 of the slot 5b indicate the disconnected, test, and connected positions respectively, only in which positions the end of the operating lever 18 can be inserted therein and removed therefrom.
The operating lever 18 can be shifted to the notched portion 5b-2 which is test position and the interim position, from the other notched portions 5b-1 or 5b-3. Test position stoppers 22 and 23 are furnished to prevent the operating lever from shifting, thereby causing the operating lever 18 to be prevented from accidental movement from the test position to the disconnected position or the connect position and causing the operating lever 18 to be prevented from directly shifting to the connect position by an overtraveling force when the operating lever is to be shifted toward the test position. When shifting the operating lever 18, it can be freely moved with the other end lifted by pushing the projection portions 22a and 23b of the stoppers 22 or 23.
In FIG. 21 the numeral 25 indicates a name-plate which shows the position of the contact operating mechanism and the contact position.
In addition, stoppers 5c and 5d (see FIG. 22.) are provided on the grip frame 5a to bring the operating rod 19 to a halt when the operating rod 19 is activated to both ends of the slot 5b and the end of the operating rod 19 has reached the notched portions 5b-1 or 5b-3. These stoppers 5c and 5d are so arranged as to contact the trapezoidal head formed at the edge of the operating rod 19, the slant side of such trapezoidal head being so designed as to contact with the stoppers 5c and 5d nearly at a right angle thereto.
FIGS. 19 and 20 respectively show the states where the contact mounting frame 9 has been moved to its test and connected positions by way of the operating lever 18.
In the test position as shown in FIG. 19, the power contact 7 is in contact with the bus bar 10 to supply power to the on board equipment of the unit frame 5, while the load contact 8 is in such a position as to be out of contact with the load side terminal 11 affording enough space for disconnection, thereby providing the power supply to the equipment to be subjected to the test without any supply to the loads.
In the connected position shown in FIG. 20, both the power contact 7 and the load contact 8 are connected to the bus bar 10 and the load side terminal 11 respectively. Thus, it is in a normal operating state.
As shown in the above, the unit frame 5 can be stored at a certain fixed position where the door 3 can be closed and blocked in relation to the panel frame 1. At this position it is possible to operate the contact mounting frame 9 to the disconnected, test, and connected positions.
An operating handle is provided on the panel surface, in order to provide ON-OFF operations of a circuit breaker built in the enclosed switchboard. In order to avoid danger a door of the enclosed switchboard can be constructed such that it can be opened only when the operating handle is set to OFF. This is completely the same in an enclosed switchboard of the above mentioned structure.
Therefore, a contact mounting frame can be shifted from a disconnected position to a test position and furthermore, to a connect position with its door closed for the sake of preventing danger when operating with the door opened, preventing invasion of foreign matter and dust to the inside and furthermore eliminating troublesome opening operations of the door.
For this reason, as shown in FIG. 2 an opening 3a is formed in the door 3 so that the slot 5b which is formed at a grip frame 5a of the unit frame 5 may be exposed to the front side and so that the operating lever 18 shown in FIG. 18 can be inserted through the opening 3a. However, if only the opening 3a is provided in the door 3, any interlocking mechanism by which the contact portion can be closed and opened only when the circuit breaker is turned off would not be feasible.